Nick Clegg is to outline on Thursday the red lines that the Liberal Democrats will demand to see in any coalition deal they negotiate with the Tories or the Labour party if a hung parliament is elected on 7 May.

Ed Miliband will revive the central pledge at the heart of Tony Blair’s landslide election victory in 1997 when he announces that a Labour government would restore the cap on class sizes for children aged five, six and seven.

The flurry of officially backed statements warning about the dangers of Brexit will come to an end on Friday, when Treasury officials enter a four-week “purdah” that prevents any activity that could be perceived as an attempt to sway the outcome of the 23 June vote.